Posted By admin On July 21, 2014 @ 5:49 pm In Articles,Features,Operations and Management,Plant Profile | No Comments

Teichert’s Hallwood Plant mines aggregate from the tailings left behind by gold-mining dredges a hundred years ago.

by Kerry Clines, Contributing Editor

Teichert Materials’ Hallwood Plant is located near the town of Marysville in northern California. It mines aggregate in the Yuba Goldfields along the banks of the Yuba River, producing crushed stone, sand, and gravel. The goldfields are estimated to contain 1 billion tons of alluvial sand and gravel, which may be the largest alluvial deposit in northern California.

The deposit

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Teichert’s Hallwood Plant is located on 711 acres of the Yuba Goldfields in northern California.

There was gold there once. The Yuba River area was originally mined by individual miners who panned for gold in the river during the beginning of the California Gold Rush in 1849. Within 10 years, large-scale hydraulic mining companies took over, blasting the riverbanks and hillsides in the Sierra Nevada Mountains with high-pressure jets of water. This type of mining creates a large amount of sediment, which filled the river and washed downstream, raising the level of the riverbed and causing floods that buried some nearby farms under mud and gravel. The sediment reached all the way to Sacramento and, eventually, as far away as San Francisco Bay. In the late 1800s, hydraulic mining came to an abrupt halt when a farmer won a lawsuit against the mining companies, but the damage was already done.

In the early 1900s, large dredges were brought in. They dug out the riverbeds, again looking for gold, and piled sediment and gravel in giant windrows along the river’s banks. This created a moonscape, of sorts, which remains to this day. The dredging helped to relieve some of the flooding problems downstream, but it also caused immense environmental damage. What was once fertile topsoil ended up on the bottom of huge piles of rocks and gravel, pretty much eliminating the possibility for any natural environmental recovery in the area.

Since then, those windrows of gravel have become a gold field, of another sort, for aggregate producers. It is a huge resource of aggregates used for construction materials, including concrete products and asphalt aggregates. The material is just sitting there in piles, waiting to be scooped up, processed, and used. So, aggregate companies, like Teichert, moved into the area.

Daily operations

“This particular site is 711 acres in the Yuba Goldfields,” says Brandon Stauffer, North Division manager, Teichert Materials, Inc. “It’s a wasteland of dredger tailings. Teichert has owned the property since the 1950s, but we didn’t start large-scale aggregate production until 1999-2000. That’s when we brought in plants and crews and started crushing up to maximum permit limits per year. Now, because of the economy, we’re only doing about one quarter of our permit limits, a fraction of what we were doing back then.”

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Wheel loaders simply scoop material from the large windrows of tailings left behind by gold dredges that mined the area in the early 1900s.

With sales being sluggish the last few years, Hallwood Plant has become very efficient. Where the operation once ran double shifts and had lots of employees, it now runs only one shift and employs about 12 people. Although sales and loadout continue year-round, the processing plant only operates for seven to nine months a year. When the processing plant shuts down at the end of the year, a month is spent making repairs to the plant equipment. Then, the crew is sent home until April 1, when the processing plant starts up again.

The water table is 5 feet below ground level. The material above the water table is basically cobbles and rocks ranging in size from 1 inch to 12 inches. High-grade sand is found below the water table.

Loaders free mine the dredger tailings above the water table. The loaders place the rock and gravel from the tailings into a feeder. From there, the material is fed onto a conveyor, which transports it to the processing plant.

The sand below the water table is mined by a dragline with a 6 1/2-cubic-yardbucket. It scoops out the sand to a depth of about 50 to 60 feet and stockpiles it. After the sand has been allowed to drain for a couple of days, a loader operator comes in, scoops it up, and places it into a second feeder. The sand is then run up to the processing plant on the same conveyor system that the rock is transported on. The products are washed, screened, crushed, and separated when they reach the processing plant.

“When the material comes into the plant, we scalp off 10-inch and larger cobbles with sidekicks and put them into a separate stockpile,” Stauffer explains. “The rest of the material goes into a primary wash screen. Everything 1-inch and smaller goes to a coarse material washer and a fine material washer. It then goes to a secondary wash plant where we make high-quality concrete sand, pea gravel, and 1-inch natural concrete aggregate. Anything 1-inch and larger goes to a crusher that reduces everything to 4-inch and smaller, which then goes to an HP500 and HP400. Everything gets reduced down to 1-inch minus and goes out to final sizing and to the different stockpiles.”

The control room in the processing plant is fully automated with all the latest in high-tech computer equipment and programs, allowing the operator to start and stop everything. He can also monitor all activities and machines to keep track of everything going on in the plant.

Customer trucks are loaded from stockpiles, as well as from silos. Yard loaders are equipped with bucket scales so the loader operator can load the trucks to 80,000 gross pounds, which is the California maximum allowable weight. If, at the scale, the truck is a bit underweight, two bins with conveyors top off the load before the driver receives his ticket.

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High-grade sand below the water table is mined to a depth of 50 to 60 feet by a dragline with a 6 1/2-cubic-yard bucket.

Hallwood Plant makes approximately 15 different products ranging in size from 12-inch cobbles to crusher dust. Five of the crushed stone products are used in the asphalt plant on site.

“The asphalt plant is a portable plant, but it has been in one location for 12 years,” Stauffer says. “We made it stationary as far as the permits go, but it’s all on wheels, so we can move it if we need to. We have three 300-ton silos to store the asphalt for our customers. Teichert Construction is one of our customers, but it isn’t our biggest customer. We supply asphalt for many of our biggest competitors, as well as for small local companies.”

In addition, used asphalt, or RAP, is recycled at the plant. Asphalt grindings from road construction jobs are brought in and stockpiled. The grindings are then crushed down and added to the asphalt mix. Caltrans (California Department of Transportation) currently allows 15 percent RAP, maximum, in its product, but Stauffer says it is working on a new Superpave spec that will allow up to 25 percent RAP in the mix once it is fractionated. “We installed a Maxim Raptor drum on our asphalt plant that will allow up to 50 percent RAP in the mix,” he adds. “We’re waiting for the state agency specs to catch up to what we’re capable of here.”

An experienced and safe crew

Stauffer raves about the crew at Hallwood Plant. “This particular group of employees has been here for 10 years,” he says. “It’s a family. It has been tough trying to keep everyone working and maintaining a positive attitude through this down economy with all the uncertainty in the world today.”

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The East Lagoon, once nothing but dredger tailings and pockets of water, was transformed by Teichert into a beautiful lake habitat surrounded by native trees and grasses.

The plant superintendent, Jim Dealba, has worked hard through the years to maintain a crew that has been cross-trained to be able to do any job in the plant, so no one has one specific job. This allows any member of the crew to do whatever is needed and to operate any piece of equipment.

Another point of pride for Stauffer, and for Teichert, is the safety record at Hallwood Plant. “We haven’t had a single lost-time injury in 11 years,” Stauffer explains. “We’ve received letters from MSHA (Mine Safety and Health Administration) recognizing the plant, and have had zero citations from MSHA at three inspections in a row several times. We had OSHA (Occupational Safety and Health Administration) and MSHA here on the same day once and got zero citations from both agencies. We also received a CalCima award a few years ago recognizing us for our outstanding safety record.

“The safety culture we’ve built here in the last 10 years is great,” Stauffer continues. “We try to treat everybody with respect, take care of each other, and watch out for each other. We operate under a Safe Production philosophy. Take the time to do things right and use the right tools for the job. We have a great group of people here. That’s a big reason why we don’t have any lost-time accidents or injuries.”

Reclamation and the environment

Teichert has been operating under vested rights in the goldfields since it purchased the land, so it isn’t required to do any major reclamation. But, the company did the right thing anyway by developing a proper reclamation plan using today’s standards.

“Teichert is a great company and always tries to do the right thing,” Stauffer says. “It goes above and beyond what the state and governing agencies require. We developed a full-blown mining and reclamation plan and are operating under the spirit of that plan today. As we mine, we take out the moonscape of dredger tailings and create open-water and shoreline habitat. We decided to mine around a few of the existing big organic areas that have a lot of trees and tie our reclamation into them.”

After an area of dredger tailings is removed, a large pond is created by the dragline as it removes the sand below the water table. When the dragline is finished, the pond is left with vertical walls and banks, so Teichert shapes and sculpts the shoreline. First, cobbles are graded and placed on the shoreline to create the proper gentle slopes going into the water. Then, a 3- to 4-foot layer of silt is placed on top of the cobbles to support vegetation. Silt is the closest thing to dirt in the area, so it is dug out of the plant’s settling ponds by the dragline, stockpiled, and hauled to the shoreline where it is dumped on top of the cobbles and graded into place.

Once the site is ready, Teichert’s restoration team and biologists come out to finish the restoration in the fall. Native plants, grasses, and wildflowers are seeded, and tree saplings are planted. The result is several different zones of habitat — emergent marsh zone, which is in the water where the frogs and small fish live; riparian wetland, where the water is very shallow; riparian upland, where the trees and brush grow; and grasslands. The site is irrigated and monitored for a period of two or three years, and progress reports are sent to the Department of Conservation.

Hallwood Plant’s first pond reclamation, the East Lagoon, began in 2003. The trees are now large and thick, the grasslands are thriving, and the wildflowers are beautiful in the spring and summer. Wildlife has returned to the area, as well. The Department of Conservation is due to make its annual inspection and is expected to sign off on the reclamation, which will mean that Teichert has successfully met all the requirements for reclamation and no longer needs to monitor the site or do anything to it.

“We’ve had a huge success with the reclamation project,” Stauffer says. “The shoreline is like a forest in some places, and the water is nice and blue. Now we’ve got something beneficial for long-term land use for wildlife and habitat. We’re proud that we’ve created something that looks so natural.”